The objective of the proposed research is to gain an understanding of the lobar division in the lungs from an elasticity point of view. An idealized axis-symmetric model of the lungs is used. The material properties for the lungs are given by a strain energy function which was derived from experimental data. The finite element method is employed to solve the Finite Elasticity problem. The interlobar surfaces (fissure) pose an unusual constraint, in that along these surfaces adjacent tissue is allowed to move tangentially with no shear stress developing. The specific aims of the proposed research are to (1) develop an algorithm to handle the unusual interlobar surface constraints, (2) compare the stress-strain state (including pleural pressure) in lungs without lobes and one with lobes, and (3) examine the effects on the stresses when a lobe is collapsed or filled with fluid. The proposed research represents the first known attempt to consider the elastic response of lungs with lobes. Both fundamental and health-related questions can be answered using this simple axis- symmetric model.